I currently use the Elementor page builder in Wordpress.
I have tried several page builders and none come close in terms of UX and ability to create pixel-perfect designs.
I am a developer and can code, but when someone asks me to create a beautiful website that they can edit themselves later without code, I ask a designer to do it in photoshop, then I pay an Elementor expert to built it and ask they don’t use any css, and usually they can make it look like the photoshop design very fast.
I can then focus on more technical features and not on the theme.
I think Elementor can be the best inspiration for TinaCMS, and if it ever gets close to it I will immediately move to JAMStack for all websites. The amount of widgets developed by the community is huge.
One think Elementor doesn’t have that is essential for intuitive design is drag and drop margins/padding, but its in this plugin:
A plugin and widget API, and shareable templates are what can make a builder really grow beyond what the core team can do.
Congrats on starting the future of theme creation!